Automatic lock for extension ladders



Feb. 11,- 1930. R. FOSS l AUTOMATIC Lox FOR EXTENSION LADnERs Filed Sept. 19. 1928 INVENTOR ATTORNEY Patented Feb. 11, 1930 TES ICE

LEE R. FOSS,` OF STOCKTON, CALIFORNIA AUTOMATIC LOCK `FOR EXTENSION LADDERS Application filed September 19, 1928. Serial No. 306,8()7.

This invention relates to extension ladders and particularly to a ladder of the form shown in PatentNo. 687,945 to S. T. Waggoner. This' ladder includes a swinging lock member mounted in connection with the movable ladder section, to automatically en-` gage and lock ontol the other section when said movable sectionis raised; and the present invention deals particularly with the means forconnectingthe locking member to n. the movable ladder section.

The principal object of this invention is to provide connection means for the purpose in the form of clampsv adapted to engage the side rails of the movable ladder section, and a single bolt for each clamp to not only cause the same to be frictionally engaged with the rail7 but forming a pivot for the locking member, and being so arranged that regardless of how much the bolt may be turned up to pro vide the necessary clamping action, the lock member cannot possibly `bind against the clamp, so that it will always have the freedom of swinging movement necessary to enable it to function properly.

A further obj ect of the invention is to produce a simple and inexpensive device and yet one which will be exceedingly effective for the purpose for which it is designed.

These objects I accomplish by means of Such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims.

In the drawings similar characters of reference indicate corresponding parts in the several views:

Fig. l is a fragmentary perspective elevation of the extension lad-der showing the improved lock supporting clamps mounted thereon.

Fig. 2 is a perspective view of one of the clamps detached. Y

Fig. 3 is a plan section showing a clamp mounted in connection with the side rails of the ladder sections.

Referring now more particularly to the characters of reference on the drawings, the ladder comprises a pair of sections arranged parallel to each other for relative extending movement, the lower or ground engaging sectionrcomprises side rails 1 and rungs 2; and the upper or movable section includes side rails 3 placed somewhat closer together than the side rails l.

The movable section is supported against downward movement relative to the lower section by vertical hanger arms 4 havinginverted U-shaped notches 5 intermediate their ends to detachably engage any rung 2, and connected at their lower ends by a rigid cross bar 6. At their Lipper ends the arms are pivotally connected to the movable ladder section, which is slidably associated with ,the lower ladder section by the same means, and this feature forms the subject matter of this invention.

The connecting members for the upper ends of the hanger arms are independent of each other and are identical in form, except that they are relatively reversed in positionso as to lie in right and left hand order.

Each such member 'comprises a horizontally disposedUU-shaped yoke 7 to closely straddle a side rail 3 of the movableladder section from the front end adjacent the lower end thereof, and another U-shaped clamp yoke 8 formed integral therewith and lying in the same horizontal plane butdisposed so that it is laterally offset from and facing at right angles to the'yoke 7 The yokeS slidably straddles the corresponding rside raill of the lower ladder section from the outside face thereof. y i

The yoke member is of malleable or somewhat yieldable metal and to positively secure v vented from being clamped against the adj acent yoke so that it could not then swingfree by reason of the fact that said bolt is pro vided, immediately under its head, with an enlarged portion l1 which engages the arm,

said enlarged portion tapering down to the ico normal diameter of the bolt for a short distance outwardly of the adjacent side of the yoke 7, or between the arm and said side as shown at 12 in F ig. 3.

It will therefore be seen that by means of this construction the bolt heads cannot approach close enough tothe yokes to bind the hanger arms thereagainst, so that the latter are always free to swing without restraint as is necessary in the successful functioning of the structure. At the same time there is nothing to interfere with the continued turning of either bolt and the accompanying drawing up of the nut thereon, to the extent necessary to firmly clamp the corresponding yoke against the ladder rail.

To rovide for a more positive and im- 4movab e support of the rails 3 in the yokes and to prevent possible rocking of the yokes on the rails, flat extensions or ears 13 project both up and down from the top and bottom edges of the yokes 7 at the front, to bear against the corresponding faces of the side rails, and thus give more area of contact with the rails than would otherwise be the case, while at the same time avoiding making the remainder of the yoke structure unduly wide and heavy. Y

From the foregoing description it will be readily seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described my invention what I claim as new and useful and desire to secure by Letters Patent is:

1. In an extension ladder comprising a pair of ladder sections one of which is movable vertically relative to the other, hanger arms to detachably engage the rungs of one section, yokes engaging the side rails of the other section, other yokes formed with and extending from said lirst named yokes for sliding engagement with the rails of said one section, and a common means for pivoting each arm to the corresponding first named yoke and for securing said yoke to its rail arranged to enable said-yoke to be clamped against the rail Without interfering with the freedom ,of swinging movement of the arm relative to the yoke.

2. In an extension ladder comprising a vpair of ladder sections one of which is movable vertically relative to the other, hanger arms to detachably engage the rungs of one section, yokes engaging the side rails of the other section, other yokes formed with and extending from said first named yokes for sliding engagement with the rails of said one section, and 'a bolt through each arm, and

the corresponding first named yoke and side rail; the head of the bolt being on the end thereof adjacent the arm and said bolt having an enlarged portion extending from the head to the adjacent side of the yoke.

3. In an extension ladder comprising a pair of ladder sections one of which is movable vertically relative to the other, hanger arms to detachably engage the rungs of one section, yokes engaging the side rails of the other section from the front face thereof, other yokes formed with and extending from said first named yokes for sliding engagement with the rails of said one section, means connecting the first named yokes to the corresponding arms and side rails, and flat eX- tensions on the backs of the first named yokes to flatly engage the front face of the rails for a certain distance above and below the plane of the top and bottom edges of the yokes proper.

In testimony whereof I affix my signature.

LEE R. FOSS. 

